Amplifying apparatus



July 21, 1925. 1,547,154 A. w. HULL AMPLIFYING APPARATUS Filed Aug. 15,1924 inventor: Albert, w. Hull His Abborn ey.

ing currents.

Patented July 21, 1925.

UNITED STATES PATENT FFIE.

ALBERT W. HULL, 0F SGHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRICCOMPANY, A CORPORATION OF NEW YORK.

AMPLIFYING APPARATUS.

Application filed August l5, 1924. Serial No. 732,284.

To all whom it may concern:

Be it known that I, ALBERT 1V. HULL, a citizen of the United States,residing at Schenectady, in the county of Schenectady, State of NewYork, have invented certain new and useful Improvements in AmplifyingApparatus, of which the following is a specification.

My present invention relates to electron discharge apparatus andcircuits" for amphfying and detecting high frequency s1gnal- One of theobjects of my invention is to provide a circuit arrangement whereby theamount of amplification which may be obtained with a single device maybegreatly increased. 5

It has been proposed in the past to em ploy a three electrode electrondischarge device for the simultaneous amplification of radio frequencycurrents and audio frequency currents. So far as I am aware however noone has heretofore proposed any practical system whereby a fourelectrode electron discharge device, particularly one i of the negativeresistance or pliodynatron type, could be employed for the simultaneousamplification of both radio and audio frequency currents.

Aqnore specific object of my invention is to provide a circuitarrangement whereby a pliodynatron may be successfullyemployed to servethe two functions-mentioned.

The novel features which I believe to be characteristic of my inventionare set forth with particularity in the appended claims,

My invention itself, however, both as to its organizationand method ofoperation will best be understood by reference to the followingdescriptiontaken in connection with the accompanying drawing in whichFig. 1 shows diagrammatically one form of my invention and Fig. 2 showsa modification thereof. p

1 have indicated in the drawing an electron discharge device 1 havingthe usual electron emitting cathode 2, plate electrode 3'and two grids 4and 5 interposed between cathode and plate. The grid 4 serves as acontrol grid and the grid 5 serves as an anode for receiving impactelectrons emitted from the plate 3. A source of potential 6 which isconnected in the circuits between I the cathode 2 and plate 3 and grid 5furnis'hes suitable values of potential for ap plication to electrodes 3and 5 to produce a of grid electrode 5.

negative resistance in the plate circuit by reason of the emission ofimpact electrons from the plate 3. By suitable adjustments the negativeresistance produced in this way may be. made great enough to compensatefor the losses of the system without at the same time causing theproduction of oscillations.

In the system shown in Fig. 1, the plate circuit may be tuned to thefrequency of the high frequency oscillations to be amplified by means ofinductance 7 and variable conof high frequency signaling currents received upon an antenna 12 and supplied by a coupling transformer13 tothe tuned input circuit 14 of device 1. Received radio frequencycurrents are amplified by device '1, rectified by crystal detector 9 andthe audio frequency currents produced by rectification supplied to theinput circuit by transformer 10, 11 and also amplified. An indication ofthe amplified audio frequency currents maybe obtained in the usualtelephone receiver 15 connected 'in the circuit By-pass condensers 16and 17 are preferably provided for bypassingaround the transformer 10,11 the radio ,frequency components of the currents flowing in thecircuit of the crystaldetector and the input circuit respectively.

In the modification of my invention, shown in Fig. 2, the detectorcircuit instead of being conductively connected to the plate circuit-iscoupled thereto by means of a condenser 18. The rectifier circuitinstead of being inductively coupled to the input circuit is coupledthereto by a resistance coupling, the audio frequency currents producedby rectification being caused to flow through a resistance 19 which isincluded in the input circuit. most satisfactory operation of the systemdescribedmay be obtained with crystal detectors whichpperate best whenslightly polarized. In the arrangement shown in Fig.

2, the adjustable contact 20 on potentiometer I have found'that the,

21 which is connected to battery 22 furnishes the desired polarizingpotential to the crystal detector 9 through a choking inductance 23. Thepotential applied to the input circuit in this way also serves as abiasing potential for the control grid 4%. In Fig. 2, I have indicatedthe inductance 7 and condenser 8 as both variable and these arepreferably so arranged that tuning of the plate circuit is accomplishedby simultaneous adjustment of both, as by this expedient the powerfactor of the plate circuit may be maintained substantially constantover a wide range of frequencies, If desired filters 24.- and 25 may beprovided at the points indicated to prevent high frequency currents fromflowing in the circuits in which they are connected.

While I have shown and described only two modifications of my invention,it will be apparent that many modifications in the particular apparatusemployed and in the manner in which it is connected in the circuit maybe made without departing from the scope of my invention as set forth inthe appended claims. I

What I claim as new and desire to secure by Letters Patent of the UnitedStates is 1. The combination in an amplifying system of an electrondischarge device having an electron emitting cathode, a plate electrodeand two grid electrodesinterposed between cathode and plate, circuitconnections between the cathode and each of the other electrodes, meansfor impressing high frequency currents to be amplified upon the circuitbetween the cathode and one of said grids, sources of potentialconnected in the circuits between the cathode and the plate and secondgrid of such value that a negative resistance is produced in the platecircuit of high enough value to compensate for the losses of the system,means for tuning the plate circuit to the frequency of the highfrequency currents, means for rectifying the amplified high frequencycurrents produced in the plate circuit, means for supplying lowfrequency currents produced by such rectification to the first gridcircuit and means for producing an indication of the amplified lowfrequency currents in the circuit of the second grid.

2. The combination in an amplifying system of an electron dischargedevice having an electron emitting cathode, a plate elec-' trode and twogrid electrodes interposed between cathode and plate, circuitconnections between the cathode and each of the other electrodes, meansfor impressing high frequency currents to be amplified upon the circuitbetween the cathode and one'of said grids, sources of potentialconnected in the circuits between the cathode and the plate and secondgrid of such value that a negative resistance is produced in the platecircuit of high enough value to compensate for the losses of the system,means for tuning the plate circuit to the frequency of the highfrequency currents, a crystal detector connected in a circuit which iscoupled to the tuned plate circuit, a coupling between the circuit ofthe crystal detector andthe circuit of the first grid and means forindicating the resultant currents produced in circuits between thecathode and the plate and second grid of such value that a negativeresistance is produced in the plate circuit of high enough value tocompensate for the losses of the system, means for tuning the platecircuit to the frequency of the high frequency: currents, a crystaldetector connected in a circuit which is coupled to the tuned platecircuit, a coupling between the circuit of the crystal detector and thecircuit of the first grid, means for indicating the resultant currentsproduced in the circuit of the second grid, and a common means forsupplying a polarizing potential to the crystal detector and a biasingpotential to the first grid.

4:. The combination in an amplifying system of an electron dischargedevice having an electron emitting cathode, a plate electrode and twogrid electrodes interposed between cathode and plate, circuitconnections between the cathode and each of the other electrodes, meansfor impressing high frequency currents to be amplified upon the circuitbetween the cathode and one of said grids, sources of potentialconnected in the circuits between the cathode and the plate and secondgrid of such value that a negative resistance is produced in the platecircuit of high enough value to compensate for the losses of the system,a variable inductance element and a variable capacity element connectedin parallel in the plate circuit, a single means for simultaneouslyadjusting both of said elements to tune the plate circuit to thefrequency of the high frequency currents means for rectifying theamplified high frequency currents produced in the plate circuit, meansfor supplying low frequency currents produced by such rectification tothe first grid circuit and means for producing an indication of theamplified low frequency currents in the circuit of the second grid. 7

5; The combination in an amplifying system of an electron dischargedevice having an electron emitting cathode, a plate elec- .trode and twogrid electrodes interposed begrids, sources of potential connected inthe .cating the resultant currents circuits between the cathode and theplate and second grid, means for tuning the plate circuit to thefrequency of the high frequency currents, means for rectifying theamplified high frequency currents produced in the plate circuit, meansfor supplying low frequency currents produced by such rectification tothe first grid circuit and means for producing an indication of theamplified low frequency currents in the circuit of the second grid.

6. The combination in anamplifying system of an electron dischargedevice having an electron emitting cathode, a plate electrode and twogrid electrodes interposed be-t tween cathode and plate, circuitconnections between the cathode and each of the other electrodes, meansfor impressing high frequency currents to-be amplified upon the circuitbetween the cathode and one of said grids, sources of potentialconnected in the circuits between the cathode and the plate and secondgrid,"means for tuning the plate circuit to the frequency of the highfrequency currents, a crystal detector connected in a circuit which iscoupled to the tuned plate circuit, a conductive coupling between thecircuit of the crystal detectorand the circuit of the first gridand'means for indiproduced in the circuit of the second grid. 7. Thecombination in an amplifying system of an electron discharge devicehaving an electron emitting cathode, a plate elecmy hand this 14th trodeand two grid electrodes interposed between cathode and plate, circuitconnections between the cathode and each of the other electrodes, meansfor impressing high frequency currents to be amplified upon the circuitbetween the cathode and one of said grids, sources of potentialconnected in the circuits between the cathode and the plate and secondgrid, means for tuning the plate plate circuit, a conductive couplingbetweenthe circuit of the crystal detector and the circuit of the firstgrid, means for indicating the resultant currents produced in thecircuit of the second grid, and a common means for supplying apolarizing potential to the crystal detector and a biasing potential tothe first grid.

8. The combination in an amplifying system of an electron dischargedevice having an electron emitting cathode, a plate electrode and twogrid electrodes interposed between cathode and plate, circuitconnections between the cathode and each of the other electrodes, meansfor impressing high fre; quency currents to be amplified upon thecircuit between the cathode and one of said grids, sources ofpotentialconnected in the circuit of the first grid and means'forindicating the resultant currents produced in the circuit of the secondgrid.

In witness whereof, I have hereunto set day of August, 1924.

ALBERT W. HULL.

